This proposal is designed to study the neuroanatomy and physiology of penile erection in monkey and dog models. The information obtained will then be used for the prevention and treatment of impotence in humans by neurostimulation. Because of socioethical reasons, impotence remains to be one of the least understood human illnesses. The etiology, differential diagnosis and prevention of this unfortunate disease are largely speculative. Our years of experience with neurostimulation have enabled us to develop a monkey model for erection studies. Sustained and controllable erection responses could be obtained even months after implantation of electrodes around the cavernous nerves in these models. Animal models will be used for these studies. 1. Physiological studies will include measurement of arterial and venous flow as well as pressures in the aorta, pudendal artery, corpora cavernosa and corpus spongiosum, during various phases of erection. This will be supplemented by pharmacologic, radiographic, and metabolic studies. 2. Neuroanatomical studies will consist of: a. Horseradish peroxidase (HRP) transport technique for identification of the spinal afferent and efferent nuclei responsible for penil erection. b. Tracing of erection nerves from the pelvic plexus to the penis by neurostimulation and microdissection. 3. Anesthesia studies will be conducted to identify suitable anesthetic procedures which do not suppress stimulated erection response. Our preliminary studies showed that suppression by inhalation anesthesia was responsible for the failure of intra-operative identification of erection nerves by neurostimulation. Therefore, proper anesthesia is essential in the prevention of iatrogenic impotence. Based on the results of these studies, we plan to submit another grant application in 2-3 years. This future application will include: 1. An erection stimulation test for differential diagnosis. 2. Using intraoperative neurostimulation to prevent iatrogenic impotence. 3. An implantable erection stimulator.